Typical optical and similar systems often employ refraction to control the propagation or distribution of excitation energy. For example, FIG. 1 shows refraction of a ray of light 90 in the visible portion of the electromagnetic spectrum at a top interface 92 and bottom interface 94 between a material 96 having index of refraction n=1 and a material 98 having index of refraction n=1.5. Due to the difference in index of refraction between the two materials 96, 98, the ray of light 90 bends at the interfaces 96, 98 between the materials.